The matrix metalloproteinase gelatinase A (MMP-2) is important in normal tissue remodeling and adaptation by its ability to degrade a broad range of tissue components. However, this enzyme has also been strongly associated with abnormal tissue degradation during inflammatory diseases (arthritis and periodontal disease), tumor expansion, and formation of metastases. Since it is significant to develop methods to inhibit the gelatinase A in disease situations, it is important to understand the molecular determinants that control proteolysis by gelatinase A. Therefore, it is the aim of the proposed studies to test the hypothesis that binding of human gelatinase A to cell surfaces via the collagen binding domain of the enzyme serves to provide a reservoir of latent enzyme and plays a role in activation of the enzyme. The first goal of this proposal is to purify and microsequence a new receptor protein from the membranes of human fibroblasts which binds gelatinase A. Based on obtained protein sequence, we will design probes that will be used to screen a cDNA library. By this screening, we will isolate a clone which encodes the cell membrane protein of interest. After isolation, the coding DNA will be sequenced and characterized. Once the cDNA clone is isolated, we will construct an expression vector that can be used to produce recombinant receptor protein in E. coli. Protein expression by this approach will permit us to obtain sufficient receptor protein to verify binding of the cellular receptor to the collagen binding domain of gelatinase A and to native gelatinase A. In addition, we will be able to fully characterize the interaction between the receptor and gelatinase A. The proposed studies should define the contribution of interaction of the new receptor protein and the collagen binding domain to cell surface localization of gelatinase A. In addition, we will gain a valuable tool for future molecular and cellular studies of gelatinase A cell surface activation mechanisms.